An endoscope system that can capture special images by changing the spectral intensity characteristics of irradiation light is known. A specific configuration of a light source device used in this type of endoscope system is disclosed in WO 2012/108420 (called “Patent Document 1” hereinafter), for example.
The endoscope system described in Patent Document 1 includes a light source device that is provided with two light emitting diodes (LEDs) and an optical filter. One of the two LEDs is a purple LED that emits light in the purple wavelength band. Also, the other LED is a fluorescent LED that has a blue LED and a yellow phosphor, and emits pseudo white light by mixing the blue LED and the yellow fluorescent light. The optical filter is a wavelength selection filter that allows only light in a specific wavelength region to pass, and can be inserted into and removed from the light path of irradiation light emitted from the fluorescent LED.
With the light source device described in Patent Document 1, when the optical filter has been removed from the light path, a subject is irradiated with light emitted from the fluorescent LED as white light, with no limitation of the wavelength band. However, when the optical filter is inserted into the light path, the wavelength band of the irradiation light emitted from the fluorescent LED is limited, and the subject is irradiated with both this irradiation light and the irradiation light emitted from the purple LED. In this way, by changing the spectral intensity characteristics of the irradiation light and irradiating the subject with only light in a specific wavelength band, it is possible to obtain a captured image in which a specific tissue inside the subject's body is emphasized.